JP5785883B2 - Heat exchanger and heat pump type water heater using the same - Google Patents

Description

  The present invention relates to a heat exchanger and a heat pump type water heater using the heat exchanger.

  Conventionally, a heat exchanger has been proposed in which a high-temperature channel for circulating a high-temperature fluid and a low-temperature channel for circulating a low-temperature fluid are both spiral structures, and the high-temperature channel and the low-temperature channel are alternately stacked (patent) Reference 1). In addition, a heat pump type hot water heater constructed by sequentially connecting a heat exchanger for hot water supply, an expansion valve, an evaporator, and a compressor with refrigerant pipes, with a high-temperature channel wrapped around the outer periphery of a helical low-temperature channel Has been proposed (see Patent Document 2).

JP 2006-125756 A JP 2009-133530 A

  By the way, in the heat exchanger comprised of a spiral channel, the flow rate outside the channel is faster than the inside, so that the heat transfer coefficient of the outer peripheral surface of the channel is the highest compared to the other surfaces. However, Patent Document 1 performs heat exchange on the upper and lower surfaces of the flow path and does not use the outer peripheral surface of the flow path, and cannot fully draw out the performance that the spiral heat exchanger can originally exhibit.

  Moreover, in the prior art of patent document 2, the high heat transfer coefficient of the outer peripheral surface of the inner flow path which is the advantage of a helical structure can be utilized by winding a high temperature flow path around the low temperature flow path. However, the inner channel where the low-temperature fluid circulates has a longer channel width in the spiral height direction than the channel width in the spiral diameter direction, and the heat transfer promotion effect by the secondary flow in the channel is not sufficient. Absent.

  Therefore, the present invention uses a heat exchanger capable of improving the heat exchange efficiency by promoting a secondary flow in the cross section of the flow path and using a portion having a particularly high heat transfer coefficient for heat exchange, and the heat exchanger. It aims at providing a heat pump type hot water heater.

The present invention includes a first heat transfer section that has a bent portion formed by bending a heat transfer tube and distributes water, and a second heat transfer section that exchanges heat with the first heat transfer section and distributes a refrigerant. The bending portion has a dimension in which a radial flow path width which is one direction among directions orthogonal to each other is larger than a flow path width in the other direction, and is opposed along the one direction. The tube wall portion of the heat transfer tube is configured to be positioned outside and inside the bent portion, and the second heat transfer portion is disposed outside the tube wall portion positioned outside.

  ADVANTAGE OF THE INVENTION According to this invention, heat exchange efficiency can be improved by using the part which accelerates | stimulates the secondary flow in a flow-path cross section, and has especially high heat transfer rate for heat exchange.

1 is a system diagram of a heat pump hot water supply apparatus according to an embodiment of the present invention. 1 is a perspective view of a heat exchanger according to Embodiment 1. FIG. 1 is a partial cross-sectional view of a heat exchanger according to Embodiment 1. FIG. 1 is an enlarged partial cross-sectional view of a heat exchanger according to Embodiment 1. FIG. 3 is a schematic diagram of a flow velocity distribution in a spiral structure according to Example 1. FIG. FIG. 3 is a schematic diagram of a secondary flow in an inner channel cross section according to the first embodiment. 4 is a graph showing the relationship between the Dean number, the flow rate, and the exchange heat amount with respect to the aspect ratio of the inner flow path according to the first embodiment. It is a fragmentary sectional view of the heat exchanger which concerns on Example 2. FIG. It is a fragmentary sectional view of the heat exchanger concerning Example 3. It is a graph which shows the relationship of the Dean number with respect to the aspect-ratio of the inner side flow path which concerns on Example 3, a flow volume, and the amount of exchange heat. It is a fragmentary sectional view of the heat exchanger concerning Example 4. It is a fragmentary sectional view of the heat exchanger concerning Example 5.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 shows a configuration of a heat pump type water heater equipped with a heat exchanger 10 according to the present embodiment. One end of the second heat transfer section 2 of the heat exchanger 10 is directed to the inlet side of the expansion valve 13, the outlet side of the expansion valve 13 is directed to the inlet side of the evaporator 12, and the outlet side of the evaporator 12 is the compressor 11. The suction side of the compressor 11 and the discharge side of the compressor 11 are connected to the other end of the second heat transfer section 2 of the heat exchanger 10.

  The operation of the heat pump type water heater of this embodiment will be described. The refrigerant 14 enclosed in the heat pump cycle is compressed by the compressor 11 to be in a high temperature / high pressure state and flows into the second heat transfer section 2 of the heat exchanger 10. The refrigerant 14 that has flowed into the heat exchanger 10 transfers heat to the water 15 that flows through the first heat transfer section 1, and the refrigerant 14 itself loses heat and flows out of the heat exchanger 10. The refrigerant 14 flowing out from the heat exchanger 10 is reduced in pressure by passing through the expansion valve 13, and heat is applied from outside air in the evaporator 12, and then flows into the compressor 11 again. In addition, the water 15 in the first heat transfer unit 1 of the heat exchanger 10 flows in a direction facing the refrigerant 14.

  Next, Example 1 will be described with reference to FIGS. The heat exchanger 10 has an appearance as shown in FIG. 3 and 4, the heat exchanger 10 includes a first heat transfer unit 1 having a bent portion R formed by bending a heat transfer tube T, and the first heat transfer unit 1. And a second heat transfer section 2 for heat exchange. In the present embodiment, the heat transfer tube T is entirely bent, and the bent portions are continuous along the flow direction over the entire first heat transfer portion 1. The bent portion R has a dimension in which the flow path width W in one direction out of the directions orthogonal to each other is equal to or larger than the flow path width H in the other direction, and the tube wall of the heat transfer tube T facing the one direction. The parts 4 and 5 are configured to be located outside and inside the bent part R. And the 2nd heat-transfer part 2 is arrange | positioned on the outer side of the tube wall part 4 located in an outer side.

  Further, the first heat transfer section 1 has a plurality of bent portions R arranged adjacent to each other, and the outer heat transfer region A is formed by the tube wall portion 4 located on the outside of each bent portion R arranged adjacent to the plurality of adjacent heat transferred portions. It is configured. The second heat transfer section 2 is disposed in the outer heat transfer area A.

  If it demonstrates concretely, the said 1st heat-transfer part 1 will be comprised by the heat-transfer tube T wound helically. When the heat transfer tube T is spirally wound, the bent portions R are continuous along the flow direction, and at the same time, the bent portions R at the same circumferential position of each layer are adjacent to each other along the height direction. That is, the 1st heat-transfer part 1 becomes a cylinder shape by winding a heat-transfer tube spirally, and the outer peripheral surface becomes the outer side heat-transfer area | region A.

  In this embodiment, the one direction that gives the flow path width W is the spiral radial direction, and the other direction that gives the flow path width H is the spiral height direction, but the direction that determines the flow path width is However, the present invention is not limited to this, and an arbitrary method is possible. For example, it does not matter whether the radial direction of the helix and the one direction or the height direction and the other direction are coincident or inclined.

  In addition, the heat exchanger 10 has a structure in which the second heat transfer section 2 is spirally wound around the outer periphery of the spiral first heat transfer section 1. Therefore, the flow path of the first heat transfer section 1 can be called an inner flow path, and the flow path of the second heat transfer section 2 can be called an outer flow path. The heat transfer tubes of the second heat transfer unit 2 are in contact with adjacent two pitch heat transfer tubes of the first heat transfer unit 1. That is, the heat transfer tubes of the second heat transfer unit 2 are arranged between the heat transfer tubes of two pitches of the first heat transfer unit 1. The cross section of the first heat transfer section 1 is formed in a rectangular shape. If it does in this way, heat conduction distance can be shortened and heat transfer efficiency can be improved.

  The flow path width W in the spiral direction and the flow path width H in the height direction are elements related to the strength of the secondary flow. 3 and 4, the flow path width W in the spiral radial direction is 1.25 times the flow path width H in the height direction. Moreover, the cross-sectional shape of the 2nd heat-transfer part 2 which contacts the 1st heat-transfer part 1 is circular. 3 and 4, the dimensions of the flow path width W and the flow path width H are taken at positions passing through the center point of the flow path cross section, but the dimensions of the flow path width W and the flow path width H are not necessarily limited. It is not necessary to take it at a position passing through the center point 3 of the channel cross section.

  FIG. 5 shows the flow velocity distribution in the spiral channel. In a flow field that swirls like a spiral channel, the flow velocity on the outer peripheral side is faster than the flow velocity on the inner peripheral side, so the velocity gradient and temperature gradient are larger on the outer peripheral side where the flow velocity is higher than on the inner peripheral side. . Therefore, the outer peripheral surface of the spiral channel has a higher heat transfer coefficient than the inner peripheral surface.

  FIG. 6 shows a flow in the cross section of the first heat transfer section 1. In the swirling flow field as shown in FIG. 5, the static pressure on the outer peripheral side of the helix is lower than the static pressure on the inner peripheral side in accordance with the law of conservation of momentum. Thereby, as shown in FIG. 6, it is composed of a flow from the inner peripheral side to the outer peripheral side through the center of the cross section of the flow path and a flow from the outer peripheral side to the inner peripheral side along the flow path wall surface. A spiral secondary flow is generated.

  The strength of the heat transfer promotion effect by the secondary flow in the channel cross section depends on the Dean number shown below.

Here, Re is the Reynolds number in the flow path, W is the flow path width in the spiral radial direction of the flow path cross section, and D _SP is the spiral winding diameter. The Reynolds number is defined as follows.

Here, U is the average flow velocity in the heat transfer tube of the first heat transfer section 1, D _h is the hydraulic diameter (= 4 × channel cross-sectional area / circumferential length), and ν is the kinematic viscosity. The hydraulic diameter of the rectangular cross section is expressed by D _h = 2WH / (W + H).

  As can be seen from Equation (1), the Dean number increases as the flow path width W in the spiral diameter direction of the flow path increases. However, when the same material usage is considered, if the flow path width W in the spiral diameter direction is increased, the flow path width H in the height direction of the spiral is reduced accordingly, so that the pump for flowing water into the flow path There is a possibility that the power consumption is increased and the performance is deteriorated when viewed as a whole heat exchanger.

In view of the above, the case where the flow velocity U is constant from the viewpoint of maintaining the pressure loss in the flow path, and the spiral winding diameter D _SP and the inner circumference L = 2 (W + H) of the cross section of the flow path are constant from the viewpoint of constant material usage. Think. If the aspect ratio of the flow path is defined as C = W / H using the flow path width W in the spiral diameter direction and the flow path width H in the spiral height direction, the flow rate Q and the Dean number are expressed by the following equations.

  A graph of equations (3) and (4) is shown in FIG. The horizontal axis represents the aspect ratio of the flow path cross section, and the vertical axis represents the ratio of the flow rate, the Dean number, and the exchange heat amount to the maximum values.

  The flow rate is maximized when the aspect ratio is 1.0, and the Dean number is maximized when the aspect ratio is 1.5. The exchange heat quantity is a product of the flow rate and the heat transfer coefficient. Further, since the heat transfer coefficient depends on the Dean number, the product of the flow rate and the Dean number corresponds to the exchange heat quantity. Therefore, it can be seen from FIG. 7 that the aspect ratio at which the exchange heat quantity is maximized for the rectangular cross section is 1.25. In this embodiment, the flow path width W in the spiral direction is set to 1.25 times the flow path width H in the height direction based on this, but the Dean number is maximized from the aspect ratio 1.0 that maximizes the flow rate. If the aspect ratio is within the range of 1.5, the performance can be sufficiently improved.

  Next, the manufacturing method of the heat exchanger 10 is demonstrated. The heat exchanger 10 is formed by first forming a circular tube into a rectangular shape and then spirally winding it to form the first heat transfer unit 1, and winding the circular tube around the outer periphery to form the second heat transfer unit 2. It forms and finally it can shape | mold easily by joining the contact part of the heat exchanger tube of the 1st heat-transfer part 1 and the 2nd heat-transfer part 2 with a brazing material.

  As described above, the heat exchanger 10 according to the present embodiment can shorten the flow path length necessary for obtaining a constant amount of exchange heat as compared with the conventional one.

  In this embodiment, the fluid flowing through the first heat transfer section 1 is water, and the fluid flowing through the second heat transfer section 2 is a refrigerant. However, the structure of this embodiment depends on the type of fluid. It is applicable.

  According to the heat exchanger of the present embodiment, the heat exchange efficiency can be improved by accelerating the secondary flow in the cross section of the flow path and using a portion having a particularly high heat transfer coefficient for heat exchange. That is, according to the heat exchanger of the present embodiment, the tube wall portions of the heat transfer tubes facing each other with the larger channel width among the channel widths in the directions orthogonal to each other are positioned outside and inside the bent portion. By configuring, the secondary flow in the cross section of the flow path can be promoted, and further, the second heat transfer section is formed on the outer surface of the tube wall section located outside the bent section, which is a portion having a particularly high heat transfer coefficient. By arranging the above, the performance of the heat exchanger can be fully utilized, and the heat transfer rate can be improved. Therefore, it is possible to shorten the flow path length necessary to obtain a certain amount of exchange heat.

  Next, Example 2 will be described with reference to FIG. Note that description of configurations common to the other embodiments is omitted. The second embodiment is different from the first embodiment in that the heat transfer tubes of the second heat transfer section 2 are brought into contact with the heat transfer tubes of one pitch of the first heat transfer section 1.

  Here, when the heat transfer tube is formed in a spiral shape, the temperature of the fluid is strictly different for each stage of the heat transfer tube. Therefore, the heat transfer tube of one heat transfer unit is connected to the heat transfer tube of the other heat transfer unit and a plurality of stages. If they are in contact with each other, the fluid temperature for each stage is averaged, and the heat exchange efficiency may be lowered depending on the method of use. In this regard, if the structure of the second embodiment is used, the heat transfer tube of the first heat transfer unit 1 and the heat transfer tube of the second heat transfer unit 2 are brought into contact with each other at only one pitch, thereby preventing a decrease in heat exchange efficiency. It becomes possible.

  Next, Example 3 will be described with reference to FIGS. Note that description of configurations common to the other embodiments is omitted. As shown in FIG. 9, this embodiment has a structure in which a heat transfer tube having a circular cross section is adopted for the first heat transfer section 1. In addition, when the aspect ratio of the 1st heat-transfer part 1 is 1.0, a heat-transfer tube becomes a circular tube, and it becomes an elliptical tube otherwise.

  FIG. 10 shows the relationship between the flow rate and the Dean number with respect to the aspect ratio of this example. The horizontal axis is the aspect ratio of the channel cross section, and the vertical axis is the ratio of each item to the maximum value. The flow rate is maximized when the cross section is circular, and the Dean number is maximized when the inner diameter 4 in the spiral radial direction is 1.31 times the inner diameter 5 in the height direction. Therefore, if the aspect ratio is in the range of 1.0 to 1.31, the exchange heat quantity can be obtained efficiently, and the maximum effect can be obtained particularly when the aspect ratio is 1.15.

  When a heat transfer tube having a circular cross section as in the present embodiment is used, the absolute values of the Dean number and flow rate are the highest values for various cross sections. Therefore, it is possible to obtain higher performance than in the first and second embodiments.

  Next, Example 4 will be described with reference to FIG. Note that description of configurations common to the other embodiments is omitted. In the heat exchanger 10 of the present embodiment, the second heat transfer section 2 is not configured by a heat transfer tube, and the flow path flows along the height direction of the helix outside the first heat transfer section 1. Is formed. If it does in this way, the area | region where the 1st heat-transfer part 1 and the 2nd heat-transfer part 2 heat-exchange can be ensured large. The second heat transfer section 2 may form a flow path between the outer peripheral surface of the first heat transfer section 1 and has a double tube structure having an inner tube and an outer tube. And the 1st heat-transfer part 1 may be arrange | positioned inside the radial direction of an inner side pipe | tube.

  Next, Example 5 will be described with reference to FIG. Note that description of configurations common to the other embodiments is omitted. The heat exchanger 10 of the present embodiment is configured by a heat transfer tube in which the second heat transfer unit 2 is arranged along the height direction of the helix outside the first heat transfer unit 1. In this way, it is possible to easily create a heat exchanger with good heat exchange efficiency without the need to spirally wind the heat transfer tube of the second heat transfer section 2.

  In addition, the heat exchanger which concerns on this invention is not limited to the structure of the said embodiment, A various change is possible within the range which does not deviate from the meaning of invention.

For example, in the above embodiment, a flow path having a circular or rectangular cross-sectional shape is assumed as the first heat transfer section 1 and the second heat transfer section 2, but some of these are combined. A cross-sectional shape having a curvature may be used. For example, an arcuate portion and a linear portion may have a continuous outer peripheral shape (so-called track shape). In addition, although it is assumed that the inner surface of the flow path is smooth, a structure in which continuous or intermittent grooves and protrusions are provided on the inner surface may be used. Furthermore, the spiral winding diameter D _SP may change in the stacking direction of the spiral structure and be formed in a tapered shape.

  For example, in the above embodiment, the first heat transfer unit 1 is described as an example in which the first heat transfer unit 1 is spirally wound. However, the first heat transfer unit has a bent portion formed by bending a heat transfer tube. If there is, the shape is not particularly limited. For example, a structure in which a bent portion is provided in a part rather than the entire first heat transfer portion 1 and the other portion is configured in another shape such as a straight portion is conceivable. Even if it is such a structure, there exists an effect because the heat exchange efficiency between the pipe wall part located in the outer side of a bending part and the said 2nd heat-transfer part can be improved. Moreover, as another example regarding the structure of the 1st heat-transfer part 1, the shape which meanders so that the outer side or inner side of a bending part may be replaced alternately may be sufficient, for example.

DESCRIPTION OF SYMBOLS 1 1st heat-transfer part 2 2nd heat-transfer part 3 Center point 4, 5 Tube wall part 10 Heat exchanger 11 Compressor 12 Evaporator 13 Expansion valve 14 Refrigerant 15 Water A Outer heat-transfer area | region _DSP spiral winding diameter H, W Channel width R Bend T Heat transfer tube

Claims (8)

A first heat transfer section having a bent portion formed by bending the heat transfer tube and circulating water;
A second heat transfer section that exchanges heat with the first heat transfer section and distributes the refrigerant;
The bent portion has a dimension in which a radial flow path width, which is one direction among directions orthogonal to each other , is larger than a flow path width in the other direction, and is a tube of a heat transfer tube facing the one direction. The wall part is configured to be located outside and inside the bent part,
The heat exchanger, wherein the second heat transfer unit is disposed outside a tube wall portion located on the outside. The heat exchanger according to claim 1,
In the first heat transfer portion, a plurality of the bent portions are arranged adjacent to each other, and an outer heat transfer region is configured by a tube wall portion positioned on the outer side of each of the bent portions arranged adjacent to each other.
The heat exchanger, wherein the second heat transfer section is disposed in the outer heat transfer area. The heat exchanger according to claim 1,
The first heat transfer section is constituted by a heat transfer tube wound in a spiral shape. The heat exchanger according to claim 1,
The bent portion of the first heat transfer section has an aspect ratio (W / H) between the channel width (W) in one direction and the channel width (H) in the other direction, the Reynolds number Re, and the heat transfer tube. Dean number (Re√ (W / D _SP )) expressed using helical winding diameter (D _SP )
Is set to be smaller than the maximum value. The heat exchanger according to claim 1,
The heat exchanger according to claim 1, wherein the channel width in the one direction is set to a size of 1.25 times the channel width in the other direction. The heat exchanger according to claim 1,
The heat exchanger according to claim 1, wherein the channel width in the one direction is set to a dimension 1.15 times the channel width in the other direction. The heat exchanger according to claim 2,
The second heat transfer part is constituted by a heat transfer tube wound in a spiral shape, and is arranged in contact with the outer peripheral side of the bent part of the first heat transfer part. The heat exchanger according to claim 1, a compressor that compresses a refrigerant flowing into the heat exchanger, an expansion mechanism that expands the refrigerant discharged from the heat exchanger, and an exhaust mechanism that is discharged from the expansion mechanism An evaporator for exchanging heat between the refrigerant and outside air,
A heat pump type hot water heater characterized in that water flows through the first heat transfer section of the heat exchanger and refrigerant flows through the second heat transfer section.